Vehicle equipped with motor and inverter

Abstract

A vehicle includes a motor for driving wheels WH, an inverter to drive the motor, and a control device to perform PWM control of the inverter. The control device performs synchronous PWM control in a case where an electric current supplied to the motor by the inverter or torque generated in the motor is larger than a threshold value; and performs the synchronous PWM control or non-synchronous PWM control in a case where the electric current or the torque is smaller than the threshold value and sets carrier frequency or a pulse number of the PWM control to be higher than the case where the electric current or the torque is larger than the threshold value. Thereby, it is possible to provide a vehicle of achieving reduction of noise, reduction of cost and improvement of fuel consumption in a balanced manner.

Description

[0001]This nonprovisional application is based on Japanese Patent Application No. 2008-218166 filed on Aug. 27, 2008 with the Japan Patent Office, the entire contents of which are hereby incorporated by reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]This invention relates to a vehicle, particularly to a vehicle equipped with an inverter to drive a motor for driving the vehicle and a control device thereof.[0004]2. Description of the Background Art[0005]In recent years, an eco-friendly vehicle to use a motor for driving the vehicle such as an electric vehicle, a hybrid vehicle and a fuel cell vehicle is drawing public attention.[0006]Japanese Patent Laying-Open No. 09-070195 discloses a control device of a motor capable of handling even in a case where rapid heat generation is caused in a switching device. In a case where a rotation speed of the motor is sufficiently low, this motor control device determines that the motor is locked by external force and sw...

AI Technical Summary

Benefits of technology

[0014]An object of this invention is to provide a vehicle of achieving reduction of noise, reduction of cost and improvement of fuel consumption in a balanced manner.

[0017]In further other aspect of this present invention, a vehicle includes a motor for driving wheels, an inverter to drive the motor, and a control device to perform pulse width modulation (PWM) control of the inverter. The control device determines carrier frequency of the PWM control so that heat generation of the inverter is minimized when an operating region of the motor defined by torque and rotation speed is a first region to protect the inverter from overheat; determines the carrier frequency of the PWM control so that noise of the motor is less detected by human when the operating region of the motor is a second region to reduce the noise of the motor; and determines the carrier frequency so that a total of a loss in the inverter and a loss in the motor is minimized when the operating region of the motor is a third region other than the first and second regions to reduce the noise of the motor.

[0019]According to the present invention, it is possible to realize the vehicle of achieving the reduction of the noise, the reduction of the cost and the improvement of the fuel consumption in a balanced manner.

Problems solved by technology

Therefore, it is not possible to sufficiently increase carrier frequency fc relative to output frequency fv in order to suppress the switching loss.

Particularly when high torque is generated, an inverter conduction loss is increased and a heat generation amount is also increased.

However, when the inverter is designed so as to drive with high carrier frequency in all operating regions, size of the inverter becomes bigger and the cost of the inverter is increased.

When carrier frequency fc is simply decreased in order to reduce the switching loss, a controllability of the motor is deteriorated.

Therefore, since there is a risk of vibration of the vehicle due to pulsation of the torque and breakage of parts due to out-of-control on an electric current, it is not allowable to simply decrease carrier frequency fc.

However, conversely at the time of low torque such as steady traveling with little noise inside the vehicle, there is a possibility that an electromagnetic sound by inverter switching is annoying.

Although frequency of the sound can be changed by changing the pulse number, it is not possible to arbitrarily change the frequency due to restriction of synchronization.

Therefore, the switching loss is increased, a problem of overheat in the inverter is caused, and hence there is a cost problem in order to prepare an inverter resistant to the above problem.

Therefore, in a case where carrier frequency fc is set to be higher than necessary, there is a possibility of an increase in the loss and a deterioration of the fuel consumption.

In other words, since too much importance is conventionally given to improvement of the controllability and the reduction of the noise, there is sometimes a case where the cost of the inverter is high and there is some room for improving the fuel consumption.

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